Variables

Variable Description
width

Width of the drawing area (screen) in pixels. This is a dynamic variable: it changes if the browser window is resized.

height

Width of the drawing area (screen) in pixels. This is a dynamic variable: it changes if the browser window is resized.

Key Words

Key Word Description & Example
if(condition) { ... } else { ... }

Standard conditional statement. else is optional. If the condition is true, the code in braces is executed.

if( x > 100 ) { print('x is greater than 100') } else { print('x is less than or equal to 100') }
static [variable] = [value]

Initialize a variable whose value will be preserved on successive loop() and animate() calls.

static i = 1 print('Die rolling attempt #' + i + ' : ' + random(1, 6)) i = i + 1 loop()

Produces:

Die rolling attempt #1 : 4 Die rolling attempt #2 : 3 Die rolling attempt #3 : 3 Die rolling attempt #4 : 3 Die rolling attempt #5 : 5 Die rolling attempt #6 : 4 Die rolling attempt #7 : 4
once { ... }

The contents of the once block are executed only once and bypassed on successive loop() and animate() calls. once is a more robust version of static. The following code blocks are equivalent:

static x = 1 static y = 2 static z = [1, 2, 3, 4, 5] once { x = 1 y = 1 z = [1, 2, 3, 4, 5] } once { x = y = 1 z = [] loop(5, i { z[i] = i }) }

Text Output

Function Description & Example
print(data, color)

Output the supplied data to the screen in a standard font. Color parameter is not required and is black by default.

print('The screen is ' + width + ' by ' + height + ' pixels.') print('Resize the browser window to see what happens!', 'red')

Canvas Operations

Function Description & Example
clear_canvas()

Clear the screen with current background color.

opacity(percent)

Set the opacity of the next and all subsequent objects to be drawn. 0 = completely transparent, 100 = completely opaque.

opacity(50)
color(color)

Set default drawing color, which is originally black.

color('yellow')
background_color(color)

Set default background (fill) color, which is originally black.

background_color('green')
line_thickness(thickness)

Set default line thickness, which is originally 1.

line_thickness(17)

Graphics Primitives

Function Description & Example
line(x0, y0, x1, y1, color, thickness)

Draw a line of the specified thickness and color between two given points. color and thickness are not required and are black and 1 respectively by default for all graphics primitives.

line(100,100, 200,200) line(0,0, width,height, 'blue') line(width/2,0, width/2,height, 'red', 40)
rectangle(x0, y0, x1, y1, color, thickness)

Draw a rectangle defined by the top left and bottom right corners.

rectangle(100,100, 200,200) rectangle(width/2,height/2, width,height, 'blue') rectangle(width/3,0, width/2,height, 'red', 40)
fill_rectangle( x0, y0, x1, y1, color, thickness)

Draw a solid (filled) rectabgle defined by the top left and bottom right corners.

fill_rectangle(100,100, 200,200) fill_rectangle( width/2,height/2, width,height, 'blue')
circle(x, y, radius, color, thickness)

Draw a circle of the specified radius centered on a given point.

circle(100,100, 80) circle(200,100, 80, 'blue') circle(width/2,height/2, height/6, 'red', 20)
fill_circle(x, y, radius, color, thickness)

Draw a solid (filled) circle of the specified radius centered on a given point.

fill_circle(100,100, 80) fill_circle(200,100, 80, 'blue')
rotate(angle)

Set the default rotation angle for regular polygons and stars.

rotate(20)
regular_polygon( x, y, radius, faces, color, thickness)

Draw a regular polygon of n faces centered on a given point.

regular_polygon(100,100, 80, 5) regular_polygon(200,100, 80, 6, 'blue')
fill_regular_polygon( x, y, radius, faces, color, thickness)

Draw a solid (filled) regular polygon of n faces centered on a given point.

fill_regular_polygon(100,100, 80, 5) fill_regular_polygon(200,100, 80, 6, 'blue')
star( x, y, radiusin, radiusout, faces, color, thickness)

Draw a star of n vertices centered on a given point.

star(100,100, 40,80, 5) star(200,100, 40,80, 6, 'blue')
fill_star( x, y, radiusin, radiusout, faces, color, thickness)

Draw a solid (filled) star of n vertices centered on a given point.

fill_star(100,100, 40,80, 5) fill_star(200,100, 40,80, 6, 'blue')

Randomness

Function Description & Example
randomize(seed)

Seed the random number generator for predictable yet still random numbers. seed argument is optional. A call to any flavor of random() after a call to randomize() produces the same random numbers on successive executions. This feature is useful during animations.

randomize() randomize(23874)
random(a, b)

Return a random number between a and b inclusively, i.e. r ∈ [a, b], if both are integers. If either of the numbers is non-integer, a floating-point number is returned between a and b exclusively, i.e. r ∈ (a, b).

random([1, 101, 201, 301, 401])

Return a random element in an array.

random(['cow', 'sheep', 'goat', 'rooster']) years = [1990, 1995, 2000, 2005, 2010] random(years);
random('color')

Return a random color.

random('red')

Return a random reddish color. Also available:

random('green') random('blue') random('yellow') random('violet') random('teal') random('gray')

Mathematics

With the exception of mod and ^, which require the second argument to be a scalar (a.k.a. number), all functions in this section take array arguments as well scalars. That is, if x is an array, then 
    f(x)
is the same as 
    [f(x0), f(x1), f(x2), ..., f(xn)]
For example: 
    x = [1, 2, 3, 4, 5]

    sq(x) →  1, 4, 9, 16, 25
Same goes for min and max. Either or both of the arguments can be arrays. 
    max(sq(x))             → 25
    max(sq(x), sq(sq(x)))  → 625
    min(sq(x), -10)        → -10
Function Description
abs(x)

Absolute value of x, a.k.a. |x|.

sin(x)

Sine of x degrees.

cos(x)

Cosine of x degrees.

tan(x)

Tangent of x degrees.

round(x)

Round x to the nearest integer, a.k.a. ||x|| or [x].

sign(x)

Return -1 if x < 0, 1 otherwise.

sqrt(x)

Square root of x, a.k.a. √x.

sq(x)

Square of x, a.k.a. x2

mod(a, b)

Modulus, a.k.a. reminder after divison of a by b. b must be a scalar.

a ^ b

a to the power of b, or ab. b must be a scalar.

min(a, b)

Return the smallest value.

max(a, b)

Return the largest value.

Loops

Function Description & Example
loop n ... end

Repeat the contents n times.

loop 10 print(random(1,10)) end loop 100 x = random(0, width) y = random(0, height) r = random(10, 50) c = random('color') fill_circle(x, y, r, c) end
loop(n, variable { ... })

Repeat the contents n while setting variable from 1 to n

loop(10, alpha { print('The square of ' + alpha + ' = ' + sq(alpha)) })
loop(start, end, step, variable { ... })

Loop the variable from start to end in increments of step. Loops can be nested.

loop(1980, 2010, 5, year { print('The year was ' + year) }) loop(0, width, width/10, x { circle(x, height/2, 50) }) step = min(width/10, height/10) loop(0, width, step, x { loop(0, height, step, y { fill_circle(x, y, step/2, random('color')) }) })
loop(delay)

Loop the entire code indefinitely, waiting delay seconds between successive executions, or 1/delay times per second. delay is 0.1s by default.